Designing an engrossing improvisational program depend as much on circumstances as the instruments used. These trios prove this by melding the relatively standard tonal colors of brass, drums and strings. Overall while the trio on Alter Egos may be a bit more exuberant, and the one on Groẞe Gartenbausstellung more restrained, the equally impressive results confirm the universality of advanced music, as does the fact that five different countries are represented on the CDs.

Oldest hand in this sort of free-form sound melding is Swedish percussionist Sven-Åke Johansson, who was playing avant-garde Jazz with the likes of saxophonist Peter Brötzmann in 1967, long before the other five players were born. An artist and a polymath, Johansson has expanded his playing strategies over the years. His scrubs and scuffs on this CD are as diffidently understated as Brötzmann sax ejaculations are still frequently bombastic. Meanwhile his partners here are two members in good standing of Berlin’s reductionist improvisers: trumpeter Axel Döner and inside-piano-specialist Andrea Neumann. The alter egos on the other CD are closer in age to one another, but diverse in nationalities. Cellist Hannah Marshall is London-born, trumpeter Ian Smith is a Dubliner who moved to London years ago, while percussionist Stephen Flinn lives in Los Angeles, but more often-than-not records with British improvisers.

Over the course of Alter Ego’s 15 tracks, Finn’s sometimes purposely muffled rhythms are not only are limited to slaps, clatters and reverberations, but also sound as if they’re coming from a berimbau, a Jew’s harp and a djembe, which may be part of the percussionist’s kit. Other approaches he uses includes the shaking of chains and ratchets, the squeaking of wetted fingers on drum tops and measured rim shots or cymbal angling that succinctly complement the others’ playing.

Marshall’s contributions to these spontaneous improvisations add to the general discordant timbres of the program. Eschewing legato, the cellist who has also collaborated with the Swiss noise-and-percussion duo Diatribes, usually plays agitato, slicing strings patterns and frequently spewing sul ponticello timbres. On a tune such as “End of Day” for instance, her wood-rending sprawls and string plinks also replicate double bass-like thumps and shimmering vibrations, as Finn rubs his drum tops in parallel cohesion. Meanwhile Smith propels his plunger notes to broken triplets and narrowed growls giving a woodwind-like lilt to his solos.

Smith, who helped institute the London Improvisers Orchestra in 1998, has steadily improved his brass skill during this century. Besides a catalogue of effects that encompass snorts, farts, slurs, puffs and noisy mouthpiece kisses, he has also internalized a command of more expected brass tropes, and can produce bugle-like brays when deemed necessary. On “Unrequited” for example his mouthpiece buzzing and osculation is designed as a counterpoint to Marshall propelling sul tasto shuffles and bow scrapes that escalate to staccato rubs and wood knocks, while Finn seconds both with wire-brush motions. Meantime “Every Instant”, one of the session’s most fully realized tunes, is built around his transformation of the brass line from pressurized grace notes to high-pitched flutter-tonguing, which somehow deepen to French horn-like pitches. Finn distinguishes himself here by bringing out his collection of miscellaneous wooden and metallic ratchets and drums, while the cellist confines herself to abstract slicing.

Dörner, who made a name for himself in groups like Die Entäuschung and with sound explorers on both sides of the Atlantic, has at his command as many extended brass techniques as Smith plus many more. Johansson, who is also listed as playing cardboard box and c-box is as subtle and sensitive a percussionist as Flinn. Moreover Neumann’s stripped-down piano harp reveals as many string timbres as Marshall does; plus Neumann unobtrusively introduces electronics to most of the CD’s nine tracks

These processed crackles and pops are most obvious on the final “Seitenausgang” where they backdrop Neumann’s mashing and bowing on her instrument’s strings plus the percussionist’s drum-top rubs which complete an exposition that commences as a pseudo sand dance and shifts to a balanced backbeat. For his part, Dörner is all over his horn switching from growling and air-blowing-without valve movements to a soupçon of lyricism, before deconstructing his solo with tremolo rumbles and tongue pops.

Puppy-like growls, cock chirps and bovine lowing are also part of the trumpeter’s brass variations, though a preference for expelling unaccented air encourages the use of protracted pauses and pregnant silences by all during the improvisations. It’s these times when Johansson minimalist box strokes are most necessary and when Neumann’s pianism is often restricted to rustling and strumming the string set. A track like “Hauptweg II” for instance is constructed out of electronic oscillations, percussion rolls, harp-like sweeps across the strings, plus Dörner’s plunger explorations accelerating to triplet-laden brassiness and then descending to buzzes deep inside his horn. In contrast “Seitenpfad” is almost fully animated. The percussionist rustles and clanks his kit and snaps his cymbals while the trumpeter matches flat-line textures with whinny smears and bugle-like extensions. For her part, Neumann’s sting pummeling probably involves the use of mallets.

Fully committed to experiments with tonal capacities, both Alter Egos and Groẞe Gartenbausstellung have created equally notable sessions.